Your analysis is the basis for an excellent discussion that should lead to the "right" decision for you.
A couple of points:
1. There is one fundamental error in your analysis:
Also the charging rating is bases on a single 12v battery or 2 6 volts in series
As I am sure you know, when two 6VDC batteries are in series the amp-hr rating of the two batteries does not change. The result is a 12VDC battery with an amp-hr rating of a single
battery in the pair.
2. The Trojan site currently states that, for FLA batteries, the charging rate should be 10% to 13% of the battery's 20 hr rate. Two T105s can therefore accept as much as 0.13 x 225 = 29.25 amps not the 56.25 amps in your tabulation. These corrections will significantly change your calculations. (It should be noted that, over the last ten years the maximum charging rate for T105s has steadily dropped from 0.25C to 0.17C and now to 0.13C)
3. I searched the entire Trojan site for the maximum charging current that their AGMs will accept to no avail. I have sent an email
to their tech support requesting this info. That said, most AGMs will accept from 0.7C to 0.8C and many can accept well above 1C. Your charge rate for AGMs must be adjusted to the correct value in order to perform a valid comparison as this is one of the biggest advantages of AGMs over FLA.
4. Nigel Calder has given seminars regarding the true, amortized cost of recharging using a genset or an alternator to charge a battery bank. As I recall
it was extremely high...dollars per amp-hr. I will try and find the source document.
As a general note; few of the AGM battery manufacturers recommend equalizing their batteries with Lifeline a notable exception.